Conventionally, cotton which is a natural fiber, and an organic fiber are used as a cut-resistant raw material, and gloves into which such a fiber and the like are knitted are widespread in fields in which cut resistance is required.
Knitted products and woven products have been suggested which are produced by using spun yarns of a high strength fiber such as an aramid fiber so as to provide cut resistance. However, the knitted products and woven products have been unsatisfactory from the standpoint of fiber detachment and durability. On the other hand, another method in which cut resistance is enhanced by using a metal fiber together with an organic fiber or a natural fiber is attempted. However, the use of a metal fiber causes texture to become hard, thereby deteriorating flexibility.
As inventions for solving the aforementioned problems, textiles and gloves in which a polyethylene fiber having a high modulus is used are suggested (for example, see Patent Literature 1). However, the modulus of the fiber is excessively high, so that an index value of the textiles and the gloves obtained in a cut resistance measurement using a coup tester is 3.8 at best as well as the texture becomes hard. Further, in the textiles and gloves, the cut resistance is improved by increasing a strength and a modulus, so that thermal conductivity is also increased. Therefore, when fresh foods are handled by, for example, meatpacking company staffs, their hands are cooled, or, on the contrary, raw materials such as meat are thawed and softened due to heat of their hands, so that, for example, the raw material cannot be cut as intended, thereby deteriorating the workability.
Further, since a color of the fiber is transparent, it is necessary to impart various colors to the fiber depending on the application in general. In order to impart a color to the fiber, a method in which a coloring component such as a pigment is blended during a spinning process step, or a method in which filaments, woven/knitted textiles, and textile products are subjected to post-processing by using dyes, are known. In the former method, there is a problem that spinning operation efficiency is deteriorated. On the other hand, in the latter method, in a case where, for example, this method is used for gloves for meat market staff handling meats, there is a concern about safety for consumers when a contained substance such as a dye is removed. Although a polyethylene is disclosed in Patent Literature 1, the polyethylene is not excellent in dyeability, so that a fiber having only a white-based color can be obtained.
Some methods for dyeing an ultrahigh molecular weight polyethylene fiber have been suggested (for example, see Patent Literature 2 to 6). In Patent Literature 2, a solvent dyeing technique for performing dyeing with an organic solvent having an oil-soluble dye dissolved therein, is disclosed. However, in this method, load on workplaces, working staff, and environments is heavy, and this technique has not been put into practical use in general.
In Patent Literature 3, an ultrahigh molecular weight polyethylene, a solvent therefor, and a technique for performing dyeing by using a dye soluble in the solvent, are disclosed. However, there are problems that, for example, (a) the number of colors that can be used is limited, (b) an imparted color becomes lighter due to a drawing process step, and (c) breakage of filaments frequently occurs during the drawing process step due to an influence of a dye applied to the surface of a fiber, so that productivity is significantly deteriorated.
Patent Literature 4 discloses a technique in which water and a dye, that is soluble in a water-soluble organic solvent, a non-water-soluble organic solvent, are used. However, since an organic solvent is used in a dyeing process step, there is a problem that environmental pollution may be caused by a dye-stained liquid. Further, since only a surface layer is dyed, fastness to washing is not sufficient. Therefore, a satisfactory colored polyethylene fiber cannot be obtained.
In Patent Literature 5, a technique for applying a dye to a highly-oriented high-molecular weight polyethylene fiber by using a supercritical fluid, is disclosed. However, since cost for introducing facilities is high, this technique cannot be adopted in general at present.
In Patent Literature 6, a technique for dyeing an ultrahigh molecular weight polyethylene fiber by using a hydrophobic dye, is disclosed. However, when the dyeing at a temperature above 100° C. is performed, dynamic physical properties of the fiber are reduced. On the other hand, when the dyeing at about 100° C. under a normal pressure is performed, the fiber can be dyed in a light color only. Further, a color fastness which is required for repeated use by washing, dry-cleaning, or the like is insufficient. Therefore, this technique cannot be practically used for a woven/knitted textile, and the like.
In Patent Literature 7, a high strength polyethylene fiber is disclosed which is used as a resin reinforcing material and a cement reinforcing material, and which has, on the surface of the fiber, a porous structure for enhancing an adhesion to a resin, a cement, and the like. However, although the polyethylene fiber described above has a high tensile strength to some degree, a thermal conductivity is high, similarly to a typical polyethylene fiber, due to the fiber containing no pores inside the fiber.
Similarly to Patent Literature 1, there are also problems including a problem that (1) when fresh foods are handled by, for example, meat market staff, their hands are cooled, and a problem that (2) raw materials such as meat are thawed and softened due to heat of their hands, so that, for example, the raw material cannot be cut as intended, therefore working efficiency is deteriorated.
Further, the fiber has a structure including a lot of pores on the surface of the fiber, thereby deteriorating cut-resistance. Thus, for example, it is difficult to practically use the fiber for a protective purpose requiring high cut-resistance.
Thus, a highly functional fiber that is excellent in heat-retaining property, cut-resistance, and dyeability, and that satisfies requirements from the market, and a protective woven/knitted textile and a cut-resistant glove using the fiber have not been completed yet at present.